A pair of optic fibers can be optically coupled by forming lenses at the ends of the optic fibers and positioning the lenses substantially in alignment and at approximately a predetermined spacing. One technique for accomplishing this, as disclosed in U.S. Pat. No. 4,497,536, is to extend the tip of the fiber beyond the front of a contact or terminus and apply heat to form the bead or lens thereon. Then the fiber is pulled back until the root of the lens rests against a locating surface at the bottom of a recess at the front of the contact, which locates the lens both laterally and longitudinally. While this technique accurately locates the root of the lens, it has the disadvantage that the lens may be broken off as it is pulled back firmly to seat its root against the locating surface. This can occur because the optic fiber and lens have very small diameters and a small force can break off the lens at or near its root.
In a lens type fiber optic connector, it is critical that the front faces of the lenses in the mating fiber optic contacts be positioned a precise predetermined distance from each other to maximize light transmission through the optical fibers joined by the contacts in a connector. This requires that the front face of the lens in each contact be positioned a precise distance from the front mating face of the contact which is half the distance desired for the spacing between the lenses in the mated contacts to assure maximum light transmission. In the prior art contact of the type described above, the position of the front face of the lens in the contact is dependent upon three tolerances namely tolerances for the axial length of the bead lens, the position of the locating surface at the bottom of the recess against which the lens seats, and the shape and location of the root of the lens. Because there are three axial tolerances applicable to the two mating contacts in a connector, there is an accumulation of manufacturing tolerances which makes it extremely difficult to achieve the proper spacing between the end faces of the lenses in the contacts necessary to avoid attenuation of the light signal through the connector.
An object of the present invention is to provide a connection apparatus and method which enables the forming and positioning of a lens at the end of an optical fiber which avoids breakage caused by pulling the fiber until the lens rests firmly against a stop.
Another object of the invention is to provide a connection apparatus and method which permits precise positioning of the end face of an optical fiber lens within a contact so that light transmission through a pair of mating contacts may be maximized.